Golf club head of ductile or gray iron

ABSTRACT

A golf club head made of a ferrous metal and having a density in the range from about 5 to about 6.8 g/cm 3  and from about 7.0 to about 7.4 g/cm 3 , and such heads made of a cast ferrous metal having a density in the range from about 5 to about 7.4 g/cm 3 . The entire golf club head may be made of such ferrous metal. Or, the ferrous metal is preferably a ductile iron or gray iron. The ferrous metal may be present as an insert in the ball hitting face of the club head, and the body of the club head may be a material different from the ferrous material. Or, the body of the club head may be made of the ferrous metal and the ball hitting face of the club head may be a different material.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/449,832, filed Feb. 27, 2003, and U.S. Provisional Patent Application Serial No. 60/507,084, filed Oct. 1, 2003, the entire disclosures of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Many conventional golf club heads and striking face inserts used in golf club heads are constructed of various materials such as steel, non-ferrous metallic alloys, titanium, aluminum, composites, plastics, rubbers, and the like. Disadvantages often associated with golf club heads and inserts made of materials conventionally utilized in the golf club making art include a “harsh” feel imparted to the golfer during and immediately after impact between the golf club head and a golf ball, poor durability, poor machinability, poor wear resistance, insufficient weight budget associated with using high-density materials in designing clubs within a specific weight constraint, significant dimensional differences between the master model and the net part resulting from the casting process, and high costs of manufacture.

[0003] Hence, the need still exists for golf club materials and designs that minimize the above-recited disadvantages and offer beneficial characteristics such as improved material damping capacity, castability, wear resistance, increased strength-to-weight ratio, reduced density relative to other ferrous materials, adequate elongation, acceptance of surface treatment and plating, a wide range of mechanical-property-manipulation capabilities, low material cost, reduced shrinkage and near-net shape casting.

BRIEF SUMMARY OF THE INVENTION

[0004] The present invention is a golf club head made from materials designed to overcome the aforementioned shortcomings and defects in prior art golf club materials and designs. The advantageous golf club head of the present invention is typically made of a ferrous metal or cast ferrous metal having a specific desired density. More specifically, that ferrous metal may be a ductile iron or gray iron. The advantageous ferrous material may be present throughout the club head, or in a portion of the club head such as an insert in the ball hitting face of a club head, wherein the remainder of the club head may be a similar or different material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The foregoing advantages and further features of the present invention will be further understood from the following drawings, which include illustrations of golf club heads which may comprise preferred embodiments of the advantageous system of the present invention, wherein FIG. 1A is a front or hitting face view of an exemplary iron-type golf club head which may embody the present invention;

[0006]FIG. 1B is another front or hitting face view of another exemplary iron-type golf club head which may embody the present invention, wherein the hitting face includes an insert;

[0007]FIG. 2A is a front or hitting face view of an-exemplary wedge-type golf club head which may embody the present invention;

[0008]FIG. 2B is another front or hitting face view of another exemplary wedge-type golf club head which may embody the present invention, wherein the hitting face includes an insert;

[0009]FIG. 3A is a front or hitting face view of an exemplary metal wood-type club head which may embody the present invention;

[0010]FIG. 3B is another front or hitting face view of another exemplary metal wood-type club head which may embody the present invention, wherein the hitting face includes an insert;

[0011]FIG. 4A is a front or hitting face view of an exemplary putter golf club head which may embody the present invention;

[0012]FIG. 4B is another front or hitting face view of another exemplary putter golf club head which may embody the present invention, wherein the hitting face includes an insert.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention relates to iron-type, wedge-type, metal wood-type or putter-type golf club heads, or inserts for such heads, comprising a ferrous metal, more particularly comprising ductile iron or gray iron. Such metals may include high nickel ductile iron, high-silicon ductile iron, annealed ductile iron, austempered ductile iron, and gray iron.

[0014] Ductile iron is a cast iron that has been treated to include magnesium, cerium, or a rare earth alloy (atomic nos. 57-71) during the casting process to cause substantially all of its graphitic carbon to take the form of spheroids or nodules within a predominantly iron-silicon matrix in the as-cast condition. In the as-cast condition, graphite nodules are suspended in a matrix of ferrite and pearlite, with the occasional presence of carbides. Using the annealing process commonly known to those skilled in the metallurgical arts, pearlite and carbides are transformed to a mostly ferrite microstructure. The newly-formed ferrite surrounds the graphite nodules formed during the casting process, and yields a moderate-strength alloy with high ductility, improved damping capacity, and approximately 10% lower density than ordinary steels.

[0015] Austempered ductile iron is a ductile cast iron that has been produced by a known controlled thermal process, which results in a matrix microstructure comprising graphite nodules suspended in predominantly acicular ferrite and high carbon austenite. This microstructure provides increased strength over as-cast or annealed ductile iron, while preserving adequate elongation.

[0016] Gray iron is a cast iron, untreated with graphite-spheroidizing inoculants, wherein substantially all of the graphitic carbon forms as flakes within a predominantly iron-silicon matrix in the as-cast condition. This flake graphite structure within the ferrous matrix provides many of the beneficial properties of the material, including outstanding damping capacity, excellent wear resistance and machinability, along with reduced density relative to other ferrous materials. The damping capacity of gray iron is as much as 125 times greater than that of ordinary steels.

[0017] Golf club heads of the present invention preferably comprise ductile iron having compositions within the following ranges of percentages by weight:

[0018] 2.8 to 4.3 wt % carbon,

[0019] 1.5 to 5.5 wt % silicon,

[0020] 0 to 1 wt % copper,

[0021] less than 0.1 wt % magnesium,

[0022] less than 0.15 wt % phosphorous,

[0023] with most of the remainder being iron.

[0024] Golf club heads of the present invention may also preferably comprise gray iron having compositions within the following ranges of percentages by weight:

[0025] 2.8 to 4.3 wt % carbon,

[0026] 1.5 to 3.5 wt % silicon,

[0027] less than 1 wt % copper,

[0028] less than 2 wt % manganese,

[0029] less than 2.5 wt % nickel,

[0030] with most of the remainder being iron.

[0031] Golf club heads of the present invention may have any of the exemplary forms schematically illustrated in FIGS. 1A through 4B. FIGS. 1A, 2A, 3A, and 4A, respectively, schematically illustrate substantially integral club heads of the iron-type 10, wedge-type 20, metal wood-type 30, and putter-type 40, respectively. FIGS. 1B, 2B, 3B, and 4B, respectively, schematically illustrate iron-type 12, wedge-type 22, metal wood-type 32, and putter-type 42 club heads, each including ball hitting face insert 14, 24, 34, 44, respectively.

[0032] Where a club head body 12, 22, 32, 42, comprises ductile iron, face insert 14, 24, 34, or 44 may comprise a different material such as a non-ferrous metal alloy, such as an aluminum alloy, magnesium alloy, or the like, a ceramic material, stainless steel, hardened steel or the like. Depending on the material composition of the insert, the insert may be press fitted into the club head body and may be welded, adhered with adhesive or otherwise bonded thereto.

[0033] In further embodiments, the entire club head body 10, 20, 30 or 40 may comprise ductile iron or gray iron, except the hosel 16, 26, 36 or 46 and/or hosel-club head body junction region 17, 27, 37 or 47, may comprise a bendable, high-elongation stainless steel or low density stainless or carbon steel, to facilitate bending of the hosel to accommodate club fitting to a particular player.

[0034] Where hitting face insert 14, 24, 34 or 44 comprises ductile iron or gray iron, club head body 12, 22, 32 or 42 may comprise a different material such as stainless steel, carbon steel, composite materials such as carbon fiber reinforced composite material, non-ferrous metal alloys such as aluminum alloys, copper alloys, manganese alloy, and the like.

[0035] Where the golf club head of the present invention comprises ductile iron, the ductile iron as cast or heat treated may have an ASTM 897 Grade selected from the group including grades 125/80/10; 150/100/07; 175/125/04; 200/155/01; and 230/185/00. Similarly, the ductile iron may have an ASTM A536 Grade selected from the group including grades 60-40-18; 65-45-12; 80-55-06; 100-70-03; and 120-90-02.

[0036] Where the golf club head of the present invention comprises gray iron, the gray iron may have an ASTM Tension Grade selected from the group including grades 20, 30, 40, 50 and 60.

[0037] The golf club heads of the present invention may comprise a ferrous metal having a density in the range from about 5 to about 6.8 g/cm³ and from about 7.0 to about 7.4 g/cm³. Such golf club heads will preferably have a density in the range greater than about 7.0 to about 7.4 g/cm³, and even more preferably in the range greater than about 7.0 to about 7.2 g/cm³. Still more preferably, such golf club heads will have a density in the range from about 7.0 to about 7.2 g/cm³, and most preferably have a density in the range from about 7.06 to about 7.1 g/cm³.

[0038] When the golf club head of the present invention comprises a cast ferrous metal, it may have a density in the range from about 5 to about 7.4 g/cm³. More preferably, that density will be in the range from about 6.5 to about 7.4 g/cm³, and even more preferably in the range from about 6.8 to about 7.2 g/cm³. Still more preferably, such golf club heads of the present invention will have density in the range from about 7.0 to about 7.2 g/cm³, and most preferably a density in the range from about 7.06 to about 7.1 g/cm³.

[0039] Where the golf club head of the present invention comprises ductile iron, the ductile iron will have a tensile strength in the range of up to about 240 ksi. Preferably, that tensile strength will be a range from about 30 to 240 ksi and more preferably in a range of about 30 to about 140 ksi, still more preferably in a range of about 30 to 100 ksi and even more preferably within a range from about 50 to about 85 ksi. The tensile strength of the ductile iron may also be in a preferable range from about 100 to about 165 ksi.

[0040] Further, when the golf club head of the present invention comprises ductile iron, the ductile iron will preferably have a 0.2% offset yield strength in the range from about 30 to about 210 ksi. More preferably, that 0.2% offset yield strength will be in the range from about 30 to 70 ksi. That 0.2% yield strength may still more preferably be in the range from about 40 to about 130 ksi, and even more preferably be in the range from about 40 to about 65 ksi. Another preferable 0.2% offset yield strength range is in the range from about 80 to about 185 ksi.

[0041] When the golf club head of the present invention comprises ductile iron, the ductile iron may have an elongation in the range up to about 28%. Preferably, that elongation will be in the range from about 4 to 25%, more preferably in the range from about 7 to about 25%, even more preferably in the range from about 12 to about 25%, and most preferably in the range from about 15 to about 25%.

[0042] Where the golf club head of the present invention comprises ductile iron, the density of the ductile iron will preferably be in the range from about 7.0 to about 7.2 g/cm³, and most preferably will be in the range from about 7.06 to about 7.1 g/cm³.

[0043] When the golf club head of the present invention is formed by casting a ductile iron material, that ductile iron should have a cast shrink rate in the range between about 0.5% and about 1%, and that cast shrink rate is preferably about 0.7%.

[0044] Where the golf club head of the present invention comprises ductile iron, the ductile iron should have a modulus of elasticity in the range from about 20 to about 25 msi. That modulus of elasticity is preferably in the range from about 22 to about 23.5 msi.

[0045] Where the golf club head of the present invention comprises ductile iron, that ductile iron should have a Poisson's ratio in the range from about 0.23 to about 0.27.

[0046] Where the golf club head of the present invention comprises ductile iron, the ductile iron should have a Brinell Hardness Number in the range from about 120 to about 810. That number will more preferably be in the range from about 300 to about 460. Another preferable range is from about 120 to about 300.

[0047] Where the golf club head of the present invention comprises ductile iron, the ductile iron material should have a vibratory decay time of 90% or less of that for typical stainless steels.

[0048] Where the golf club head of the present invention comprises gray iron, the gray iron should have a density in the range from about 7.0 to about 7.3 g/cm³, and preferably in the range from about 7.1 to about 7.2 g/cm³.

[0049] Where the golf club head of the present invention comprises gray iron, the tensile strength of the gray iron should be in the range up to 80 ksi, preferably in the range from about 15 to about 60 ksi, and even more preferably in the range from about 20 to about 40 ksi.

[0050] Where the golf club head of the present invention comprises gray iron, the gray iron should have a modulus of elasticity in the range from about 10 to about 25 msi.

[0051] Where the golf club head of the present invention comprises gray iron, the gray iron should have a Brinell Hardness Number in the range from about 100 to 350, and preferably in the range from about 100 to about 250.

[0052] Where the golf club head of the present invention comprises gray iron, the gray iron should have a vibratory damping capacity that is 2 to 125 times that of ordinary stainless steels.

[0053] The advantageous materials of the present invention have an increased strength-to-weight ratio, a relatively low density, adequate elongation characteristics and relatively low cost vis-à-vis other club head materials. When used in the desired club head manufacturing techniques, these materials exhibit excellent castability with minimal shrinkage and thus minimal net dimensional differences between the club head master model and the net part resulting from the casting process. They also exhibit good machinability to facilitate final shaping and finishing, and a wide range of mechanical property manipulation capabilities through composition variations and heat treatment techniques. And, these manufacturing advantages are achievable at lower manufacturing costs.

[0054] Thus, the club heads of the present invention manufactured from ductile iron or gray iron material enjoy the advantages of excellent durability and wear resistance presented by those materials. Furthermore, golf clubs according to the present invention possess improved wear-resistance characteristics associated with comparatively-great hardness values of annealed ductile iron, austempered ductile iron, and gray iron, whose measured hardness is comparable to, and in many cases greater than, that of typical carbon or stainless steels.

[0055] Ultimately, the excellent damping capacity and other characteristics of these materials provide the inventive club heads made therefrom the ability to exhibit excellent “feel” to the golfer using such clubs, both during and immediately after such an inventive club head impacts a golf ball. The current understanding and expectation in the golf club-making art is that a perceived “soft” feel at impact with the ball is generally related to the measured hardness of the club-head material—the greater the material hardness, the “harsher” the feel, and vice versa. However, in spite of comparatively-great hardness values, the enhanced material damping capacity and reduced density (which permits advantageous localization of mass) of ductile iron or gray iron provide an unexpected noticeable improvement in feel, at ball impact, to the golfer. This improvement in feel is beyond the typical correlation to measured hardness expected by those skilled in the golf club-making art.

[0056] Those skilled in the art of golf club manufacture will appreciate that minor changes in the details of the present invention can be made without departing from the scope and spirit of the invention which is defined by the following claims. 

What is claimed is:
 1. A golf club head comprising a cast ferrous metal having a density in the range from about 5 to about 7.4 g/cm³.
 2. A golf club head comprising a ferrous metal and having a density in the range from about 5 to about 6.8 g/cm³ and from about 7.0 to about 7.4 g/cm³.
 3. The golf club head of either of claims 1 or 2, wherein the ferrous metal is present in the form of an insert in the ball hitting face of the club head.
 4. The golf club head of either of claims 1 or 2, wherein the body of the club head comprises a material different from the ferrous material.
 5. The golf club head of either of claims 1 or 2, wherein the body of the club head comprises the ferrous metal and the ball hitting face of the club head comprises a different material.
 6. The golf club head of claim 5, wherein the ball hitting face includes an insert which comprises a material selected from the group consisting of non-ferrous metal alloys, aluminum alloys, magnesium alloys, copper alloys, manganese alloys, ceramic materials, stainless steel, carbon steel, hardened steel, non-metallic composite materials, and carbon fiber reinforced materials.
 7. The golf club head of claim 5, wherein the ball hitting face includes an insert which comprises the different material, and at least one of the hosel portion and club head body/hosel junction portion of the club head comprises a material that is more bendable than the remainder of the club head body.
 8. The golf club head of claim 2, having a density in the range greater than 7.0 to 7.4 g/cm³.
 9. The golf club head of either of claims 1 or 2, having a density in the range from about 7.0 to about 7.2 g/cm³.
 10. The golf club head of either of claims 1 or 2, having a density in the range from about 7.06 to about 7.1 g/cm³.
 11. A golf club head comprising ductile iron.
 12. The golf club head of claim 11, wherein the ductile iron is selected from the group consisting of high-nickel ductile iron, high-silicon ductile iron, annealed ductile iron, and austempered ductile iron.
 13. The golf club head of either of claims 11 and 12, wherein the ductile iron is present in the form of an insert in the ball hitting face of the club head.
 14. The golf club head of claim 13, wherein the body of the club head comprises a material different from the ductile iron.
 15. The golf club head of either of claims 11 and 12, wherein the body of the club head comprises ductile iron and the ball hitting face of the club head comprises a different material.
 16. The golf club head of either of claims 11 and 12, wherein the ductile iron has a tensile strength in the range up to about 240 ksi.
 17. The golf club head of claim 16, wherein the tensile strength is in the range of from about 30 to about 240 ksi.
 18. The golf club head of claim 17, wherein the tensile strength is in the range of from about 30 to about 140 ksi.
 19. The golf club head of claim 17, wherein the tensile strength is in the range of from about 30 to about 100 ksi.
 20. The golf club head of claim 17, wherein the tensile strength is in the range of from about 50 to about 85 ksi.
 21. The golf club head of claim 17, wherein the tensile strength is in the range of from about 100 to about 165 ksi.
 22. The golf club head of either of claims 11 and 12, wherein the ductile iron has a 0.2% offset yield strength in the range from about 30 to about 210 ksi.
 23. The golf club head of claim 22, wherein the 0.2% offset yield strength is in the range from about 30 to about 70 ksi.
 24. The golf club head of claim 22, wherein the 0.2% offset yield strength is in the range from about 40 to about 65 ksi.
 25. The golf club head of claim 22, wherein the 0.2% offset yield strength is in the range from about 40 to about 130 ksi.
 26. The golf club head of claim 22, wherein the 0.2% offset yield strength is in the range from about 80 to about 185 ksi.
 27. The golf club head of either of claims 11 and 12, wherein the ductile iron has an elongation in the range up to 28%.
 28. The golf club head of claim 27, wherein the elongation is in the range from about 4 to about 28%.
 29. The golf club head of claim 28, wherein the elongation is in the range from about 7 to about 25%.
 30. The golf club head of claim 27, wherein the elongation is in the range from about 12 to about 25%.
 31. The golf club head of claim 28, wherein the elongation is in the range from about 15 to 25%.
 32. The golf club head of either of claims 11 and 12, wherein the ductile iron has an ASTM 897 Grade selected from the group consisting of 125/80/10; 150/100/07; 175/125/04; 200/155/01; and 230/185/00.
 33. The golf club head of either of claims 11 and 12, wherein the ductile iron has an ASTM A536 Grade selected from the group consisting of 60-40-18; 65-45-12; 80-55-06; 100-70-03; and 120-90-02.
 34. The golf club head of either of claims 11 and 12, wherein the ductile iron has a density in the range from about 7.0 to about 7.2 g/cm³.
 35. The golf club head of claim 34, wherein the density is in the range from about 7.06 to about 7.1 g/cm³.
 36. The golf club head of either of claims 11 and 12, wherein the ductile iron has a vibratory decay time of 90% or less of that for stainless steel.
 37. A golf club head of either of claims 11 and 12, wherein the ductile iron has a cast shrink rate of between about 0.5% and about 1%.
 38. A golf club head of claim 37, wherein the cast shrink rate is about 0.7%.
 39. The golf club head of either of claims 11 and 12, wherein the ductile iron has a modulus of elasticity in the range from about 20 to about 28 msi.
 40. The golf club head of claim 39, wherein the modulus of elasticity is in the range from about 22 to about 26 msi.
 41. The golf club head of either of claims 11 and 12, wherein the ductile iron has a Poisson's ratio in the range from about 0.23 to about 0.27.
 42. The golf club head of either of claims 11 and 12, wherein the ductile iron has a Brinell Hardness Number in range from about 120 to about
 810. 43. The golf club head of claim 42, wherein the Brinell Hardness Number is in the range from about 300 to about
 460. 44. The golf club head of claim 42, wherein the Brinell Hardness Number is in the range from about 120 to about
 300. 45. The golf club head of either of claims 11 and 12, wherein the ductile iron has a chemical composition by weight within the ranges: 2.8 to 4.3 wt % carbon, 1.5 to 5.5 wt % silicon, 0 to 1 wt % copper, less than 0.1 wt % magnesium, less than 0.15 wt % phosphorous, with most of the remainder being iron.
 46. A golf club head comprising gray iron.
 47. The golf club head of claim 46, wherein the gray iron is present in the form of an insert in the ball hitting face of the club head.
 48. The golf club of claim 47, wherein the ball hitting face insert comprising gray iron is attached to a recessed or open portion of the golf club head.
 49. The golf club head of claim 48, wherein the face insert is attached to the club head by a means selected from the group consisting of: a weld, a mechanical locking fit, an adhesive bond, an adhesive tape bond, and any combination thereof.
 50. The golf club head of claim 47, wherein the body of the club head comprises a material different from the gray iron.
 51. The golf club head of claim 46, wherein the body of the club head comprises gray iron and the ball hitting face of the club head comprises a different material.
 52. The golf club head of claim 46, wherein the gray iron has a tensile strength in the range up to 80 ksi.
 53. The golf club head of claim 52, wherein the gray iron has a tensile strength in the range from about 15 to about 60 ksi.
 54. The golf club head of claim 52, wherein the gray iron has a tensile strength in the range from about 20 to about 40 ksi.
 55. The golf club head of claim 46, wherein the gray iron has an ASTM Tension Grade selected from the group consisting of 20, 30, 40, 50, and
 60. 56. The golf club head of claim 46, wherein the gray iron has a density in the range from about 7.0 to about 7.3 g/cm³.
 57. The golf club head of claim 49, wherein the density is in the range from about 7.1 to about 7.2 g/cm³.
 58. The golf club head of claim 46, wherein the gray iron has a damping capacity that is 2 to 125 times that of stainless steel.
 59. The golf club head of claim 46, wherein the gray iron has a modulus of elasticity in the range from about 10 to about 25 msi.
 60. The golf club head of claim 46, wherein the gray iron has a Brinell Hardness Number in the range from about 100 to about
 350. 61. The golf club head of claim 60, wherein the Brinell Hardness Number is in the range from about 100 to about
 250. 62. The golf club head of claim 46, wherein the gray iron has a chemical composition by weight within the ranges: 2.8 to 4.3 wt % carbon, 1.5 to 3.5 wt % silicon, less than 1 wt % copper, less than 2 wt % manganese, less than 2.5 wt % nickel, with most of the remainder being iron. 